To permit the axially tandem-mounted screw elements to intermesh tightly on the axis-parallel shafts of such a machine, they must be positioned reliably on the shafts in the axial direction with the highest precision. For this purpose the screw elements are disposed in axially displaceable fashion on the shaft, e.g. with a splining, and connected with the shaft so as to rotate in unison. The screw elements are tightly prestressed axially on the shaft, with the shaft tip, which is accordingly formed as a screw bolt, screwed into an axial threaded bore in the shaft end.
The stop can be formed, for example, by a collar created by turning off the shaft on the lathe. Since such a collar involves enormous production effort, it is also known to provide the shaft with a ring groove receiving a split stop ring. However, such a stop ring in a ring groove of the shaft does not allow the desired precision to be attained in view of the high axial loads acting on the screw shafts, in particular, the high axial pressure.